Children, parents and pets exercising together (CPET): exploratory randomised controlled trial

Levels of objectively measured moderate-vigorous intensity physical activity (MVPA) are much lower than recommended in UK children [1–4], a worrying observation considering that MVPA is associated with numerous health benefits including significant improvements in blood lipids, BMI and body fatness [5]. Recent evidence from the UK suggests that objectively measured PA declines and sedentary behaviour increases before adolescence [4–7]. Furthermore, the incidence of obesity and the degree of excessive weight gain in those who do not become obese is greatest in mid-late childhood (ages 7–11 years old) [8, 9]. Recent reviews of interventions to promote PA in children have questioned both the magnitude and sustainability of intervention effects [10–12]. Few family/home based interventions have been carried out to date [13, 14], even though some family and home factors are associated with low levels of objectively measured PA in mid-late childhood [13–15]. Therefore, there is an opportunity for novel approaches to the promotion of PA in mid-late childhood incorporating a family/home based intervention.

A study protocol paper has been published detailing the rationale, study design and methods of the Children, Parents and Pets Exercising Together (CPET) exploratory randomised controlled trial (RCT) [16]. Briefly, the use of pet dogs represents a potentially valuable and underutilised opportunity to promote PA in children and their families [17]. In Scotland there are approximately 800,000 dogs and 360,000 children of primary school age, with UK dog ownership estimated at around 22-24% of households with higher dog ownership among families of lower socio-economic status [18]. A number of cross sectional studies have shown that PA levels are higher in adults who walk their dogs regularly [19] and in children who own a dog [20, 21]. However, in one Australian study only 23% of 5–6 year olds and 37% of 10–12 year olds ever walked with their dog [22]. Moreover, a recent North American study found that adult dog owners receiving a low intensity dog walking intervention focused on the benefits of walking the dog increased their PA levels more than owners who did not receive the intervention [23]. In summary, promotion of more walking and play with the dog could be a useful strategy to promote family, and in particular, child PA.

There is a dearth of objective information on the type of dog walking by owners and their families; previous estimates of the frequency and duration of dog walking are derived solely from subjective measures such as questionnaires. One recent Australian study found that only 23% of owners walked their dog 5 or more times per week [24] and a study in North America found, that among those who reported walking their dog, the median frequency was 3 times per week with a median duration of 25 minutes [25]. Another Australian study found that children who owned a dog walked the dog on average 1.7 times per week and 32% of owners reported that they rarely or never walked their dog as a family [22]. None of these studies measured dog walking objectively or assessed the intensity of PA achieved during dog walking, an important consideration for maximal health benefits. The present exploratory trial was intended to improve our understanding of the frequency, intensity and duration of dog walking among dog owning families in Scotland.

The UK Medical Research Council Framework for the development and evaluation of complex interventions in public health [26] recommends that definitive trials should be preceded by exploratory trials to provide information about the design, feasibility and acceptability of a trial and intervention. Information regarding the delivery of the intervention, recruitment and retention rates, and effect sizes of outcomes can also be gleaned to help inform future more definitive trials. For example, a recent pilot study exploring the feasibility and acceptability of an intervention aimed at promoting movement skill and PA in children found that recruitment and retention rates, collection of outcome data and delivery of intervention sessions were all high, and staff involved in implementing the intervention reported high satisfaction with the program [27]. In contrast a feasibility study evaluating an adolescent sexual health intervention found that the intervention was unlikely to be deliverable, leading to substantial changes to both the content and delivery of the original intervention [28]. Therefore, an exploratory evaluation of an intervention is required to ensure that subsequent interventions are appropriately designed and developed.

The aim of this paper is to report on the feasibility of the CPET intervention and trial, the acceptability of the trial and intervention, preliminary evidence of its potential efficacy, planning and powering a future intervention, and to improve our understanding of the frequency, intensity and duration of dog walking among dog owning families in Scotland.

The following section is a brief account of the study design/methods. For a more detailed description see the study protocol paper [16].

Trial feasibility

Study sample, recruitment, and inclusion criteria

Invitation letters were sent to approximately 350 dog-owning parents with children attending mainstream primary schools in one local authority area, East Dunbartonshire, in the West of Scotland. Families that responded to the letter were included only if they met the inclusion criteria [16]. Parents were asked to complete a dog behaviour screening questionnaire developed by two members of the Association of Pet Behaviour Counsellors (Westgarth and Hutchison) which assessed whether it was appropriate for each dog to take part in the study. Dogs that did not pass the screening questionnaire and those which were physically unable to take part were excluded. Finally, a CONSORT study flow diagram [29] (Figure 1) was used to summarise sample attrition and missing data for all of the outcome measures. Data on exclusion, recruitment, retention, number of missed intervention sessions and number of completed outcome measures are provided as an indicator of trial feasibility. The Carstairs Score [30] was used as a proxy for socio-economic status of study participants. The Carstairs score is a deprivation measure deriving from UK census data and each postcode area is classified into a deprivation category (DEPCAT for short) ranging from 1 (most affluent) to 7 (most deprived).

To our knowledge this is the first RCT to assess the feasibility, acceptability and potential efficacy of a dog-based PA intervention in children and their families. CPET was an exploratory, assessor-blinded RCT as recommended in the UK MRC framework for developing and evaluating complex interventions [26], and was developed to inform a future more ‘definitive’ trial. The results show that the CPET trial was feasible and the intervention was acceptable to participants. Eighty-nine per cent of families were retained in the present study and greater than 90% of data were collected for all outcome measures except those deriving from DXA scans. Children and parents who participated in the intervention group agreed that the outcome measures and intervention content were acceptable. Despite this, there was no significant change in the primary outcome measure (child PA) or the majority of the secondary measures (parent and dog PA, child BMI, bone health and health related quality of life). Furthermore, small effect sizes were found for our primary outcome measure and all secondary outcome measures except total volume of PA in dogs and the amount of time they spent in vigorous intensity PA.

The retention rates in CPET are comparable to those reported in other PA studies in children and their families. Chen et al. [44] retained 85% of participants at follow up and Sacher et al. [45] reported that 90% of children randomised to a 9 week intervention were available at the end of the intervention. Few family based studies have reported the level of adherence to the intervention programme. Morgan et al. [46] reported that 81% of intervention sessions were attended and Sacher et al. [45] reported that 86% of sessions were attended during the intervention. The level of adherence to the CPET intervention programme and the results from our qualitative study suggest that acceptability of the outcome measures and intervention content was high. One possible explanation for the high rate of adherence to the intervention in CPET may be that all intervention sessions were home/telephone based whereas other intervention programmes have required attendance at group sessions outside the home [45, 46]. The CPET intervention was therefore flexible in terms of delivery, participants were not required to travel in order to receive the intervention and all intervention sessions were delivered to suit the availability of participants.

The number of completed outcome measures in CPET was high for all outcomes except measurement of fat mass, lean mass and bone mineral content in children. Body weight, BMI, BCS and child health related quality of life data were collected for all participants at baseline and all available participants at follow up, indicating that feasibility of collecting these outcomes was high. Furthermore objectively measured PA data were collected on all children at baseline and all those available at follow up. PA data was collected on all but one parent and dog at baseline, and all but one parent and dog that were available at follow up. One reason why only 82% of DXA related outcome data was collected at baseline and from 84% of the available children at follow up was because participants were asked to attend a local children’s hospital to have DXA scans carried out but only limited appointments were after school hours. Some participants were therefore unable to make a suitable appointment due to other commitments.

Although a dog-walking intervention such as CPET may be both feasible and acceptable on a small scale and in the short term, the relatively low conversion of expressions of interest (n = 127) into signed consent (n = 36) suggests that alternative methods of recruitment may be required to implement CPET on a larger scale. Prior to a definitive trial a formative evaluation of the reasons why those who initially expressed an interest and subsequently did not choose to take part in the study might highlight reasons for the low conversion rate. It may be that the expansion of CPET will require recruitment to be carried out over a larger area with access to more potential participants. Alternatively a completely different approach to recruitment such as advertising in local media or veterinary practices may be necessary. The primary concern with regards to recruitment was a potentially high rate of exclusion due to behavioural issues with dogs, however this did not seem to be the case as only 1 of the 36 families who consented to participation was excluded for this reason.

No statistically significant differences in either the number or duration of dog walks, or child or parent PA during periods of dog walking were detected and effect sizes were small for all outcomes. However, a statistically significant difference in the amount of time dogs spent in vigorous intensity PA during dog walks was found. It should be noted that although this was statistically significant, it equates to a mean difference of ~ 2 minutes during total dog walking time for the week, and is therefore unlikely to be of any biological significance. If the number of dog walks in intervention families had increased however, the amount of time dogs spent in vigorous intensity PA may have been much greater. Previous reports on the amount of family dog walking have relied on subjective measures such as questionnaires [22], which are often subject to response bias [47, 48]. The present study presents data not only on the amount but the intensity at which dog walking takes place among families and suggests that dogs are walked 2–3 times per week as a family when measured objectively. This suggests that in our sample family dog walking was more common than elsewhere, with one Australian study reporting that when measured subjectively family dog walking took place at most once or twice per month [22]. Nevertheless, the amount of family dog walking in this study was still low considering that the average total duration per week for the sample as a whole was 41 minutes at baseline and 37 minutes at follow up. Despite no significant increase in PA being observed due to the intervention, the extent to which dog walking might contribute to accumulated MVPA in children and/or their parents suggests that increasing the frequency and duration of dog walking is a promising strategy for increasing PA in families. Children spent between 15 and 26% of family dog walking time in MVPA compared to only 3% of total wear time; parents spent between 20 and 45% of dog walking time in MVPA compared to between 5 and 7% of total wear time; and dogs spent 13-25% of dog walking time in vigorous intensity PA compared to only 1-2% of total wear time. This suggests that, if carried out for a sufficient duration, family dog walking represents an opportunity to increase MVPA across the whole family and might in future be valuable for PA promotion more widely. The amount of time spent sedentary or physically active can vary widely depending on the cut point used to define intensities of PA in both children and adults [49], it is therefore difficult to say with certainty that periods when the parent, child and dog were all being physically active together were correctly identified.

Although effect sizes were small for our primary outcome measure (total volume of PA in children) they were not too dissimilar to many other PA interventions in children. A recent meta-analysis [50] which assessed the effectiveness of 30 PA interventions where PA was measured objectively (i.e., accelerometry) concluded that such interventions have had a small to negligible effect on total volume of PA (d = 0.12) and with only small increases in MVPA, ~ 4 minutes per day (d = 0.16). The CPET intervention resulted in a mean difference in total volume of PA of 30 cpm in children (d = 0.21) and a mean difference in MVPA of ~ 2 mins/day (d = 0.20), although given the lack of power in the present study it is questionable whether these differences are real. In contrast the effect sizes reported here for PA in parents did not compare favourably with other PA interventions in adults, with a recent review [51] concluding that the pooled intervention effect on overall PA between intervention and control groups was small (d = 0.19). The results for the efficacy of the intervention on dogs were more positive, with medium to large effect sizes reported for total volume of PA (mean difference of 79 cpm, d = 0.71) and vigorous intensity PA (mean difference of ~ 6 minutes/day, d = 0.70). To our knowledge there are no published studies assessing the efficacy of a PA intervention on objectively measured PA levels of pet dogs and therefore comparison with other studies is not possible. Furthermore, the biological significance of an increase in vigorous intensity behaviour of 6 minutes/day in dogs is unclear.

There are no comparable studies assessing the efficacy of a dog walking intervention on PA in children, although there are two published studies assessing the efficacy of a dog walking programme in adults. Kushner et al. [52] reported that overweight adults taking part in a 16 week intervention with pet dogs had significant increases in PA and significant decreases in body weight. PA was not measured objectively and this was a clinical trial in overweight adults, and it is therefore difficult to make comparisons with CPET. Rhodes et al. [23] carried out a pilot study of a dog walking intervention in adults who did not regularly walk their dog: their intervention appears to have resulted in significantly higher step counts compared to control. In contrast CPET did not result in an increase in objectively measured PA in either children or their parents, or the number or duration of dog walks. In the present study children and their parents were asked to participate in dog walking/active play with the dog together and this may be logistically more difficult than asking a lone adult to increase dog walking time and thus PA [23]. In addition, dogs were already being walked at baseline and a number of parents taking part in CPET noted at baseline that it was difficult for them to change their habits of dog walking. These parents liked to walk the dog early in the morning or late at night, i.e. when their child would be less likely to take part. Future dog walking interventions should attempt to help families reduce barriers (e.g., time) and create more opportunities for additional dog-walking opportunities as a family.

Despite the overall lack of effect that CPET had on PA outcomes the results of the qualitative study were promising. The vast majority of parents in the intervention group agreed that the intervention content was sufficient to motivate them and their children to increase PA through dog walking. In addition, children who took part in the focus groups highlighted that they enjoyed taking part in CPET and felt that they increased the amount of PA they did. Similarly parents who took part in the focus groups suggested that they had experienced longer family walks. Key stakeholders interviewed as part of the qualitative study suggested that it may be difficult to motivate families from less affluent areas to take part. The distribution of DEPCAT scores among the study population suggests that this was not an issue in this study. Ninety-six percent (27/28) of CPET families were classified as DEPCAT 1, 2 or 3 compared to 87% of the population of East Dunbartonshire and 42% of the population of Scotland [30]. This all suggests that motivation was not a factor in the lack of change in PA.

It is possible that the short duration of the intervention prevented an increase in PA in the intervention group compared to controls and a future more definitive trial should include an intervention period of longer than 10 weeks. It may also be possible that intervention families did increase PA during the intervention as suggested in the focus groups but failed to maintain this when PA was measured post intervention. Future trials should, if possible, measure PA multiple times, i.e. at baseline, mid-intervention and post intervention, for longer periods i.e. 2 weeks instead of 1, or even continuously throughout the intervention period to overcome this, although the increased burden of wearing accelerometers for longer periods may not be acceptable to participants. Continuous or multiple measurement of PA would also help overcome any effect of variations in weather. Clearly adverse weather conditions can have an effect on outdoor PA and data from the nearest UK Met Office weather station to the geographical area where the intervention took place estimates that rainfall in the period when many of the post intervention measurements were taken was almost double that at baseline [53]. The failure to detect any significant changes in child or parent PA may also have been due to PA compensation, the theory that study participants may compensate for imposed bouts of PA by reducing PA at other times [54, 55]. This was highlighted by some of the parents who took part in the focus groups who suggested that CPET had replaced other forms of PA. Future studies should therefore highlight the importance of maintaining other forms of PA while also increasing the amount of dog walking.

This study had a number of strengths and limitations. First, it was an exploratory randomised controlled trial as set out in the CONSORT statement [29] and the UK Medical Research Council Framework for the development and evaluation of complex interventions in public health [26]. Second, trained blinded assessors were used to carry out the outcome measures and were independent of the research assistant who delivered the intervention. Furthermore, the study methods included validated instruments for measuring our primary and secondary outcomes, including the objective measurement of PA. Although it was not one of our aims to recruit a large sample size, the relatively small sample size prevented assessment of any effects of the intervention on boys and girls separately, or by type of dog owned (breed, age etc.) and is symptomatic of an exploratory trial. The small sample size also prevented conclusions with any certainty as to whether any of the small differences found are real. In addition, the intervention at this stage was resource intense to deliver (for example using a session with a qualified behaviourist). This study was designed as an exploratory RCT that will inform the design of a future, larger and longer term trial, not to report solely on the potential efficacy of such a study. Studies of this nature are needed to determine if dog based PA interventions have any effect on habitual PA over the longer term. Since outcomes were measured in the period immediately after the intervention rather than during the final week this might have reduced any apparent impact of the intervention.

This study suggests that using pet dogs as the agent of lifestyle change in PA interventions in children and their parents is both feasible and acceptable. These results will be used to inform the design, development and implementation of future, larger scale trials.